JP2007009104A - White phosphor and method for producing the same and white luminescent element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a white phosphor exhibiting luminescence in the vicinity of 420 nm wavelength, the vicinity of 540 nm wavelength and the vicinity of 610 nm wavelength as is clear from fluorescence spectra and exhibiting luminescence having good color-rendering properties and including a blue component, a green component and a red component, a white phosphor containing CaZrO<SB>3</SB>as a single crystal matrix, being free from mutual action and not applying load to production, a white phosphor excellent in reliability and environmental resistance, a white phosphor capable of applying to general illumination in which white light close to natural light (solar light) is required and a white phosphor which is expectable in display field and also as back light for liquid crystal and a phosphor for PDP, EL, FED and CRT. <P>SOLUTION: The white phosphor represented by general formula (1): Ca<SB>x</SB>Zr<SB>y</SB>O<SB>3</SB>:Eu, Tb (wherein 0.8≤x/y≤2.0) is preferably adopted. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a white phosphor capable of emitting white light with a single base material and a white light emitting device using the same. More specifically, a conventional white light emitting element such as a light emitting diode that provides three light components of red, green, and blue is provided in close proximity to each other to emit light, and then diffuse and mix to generate white light. Unlike a light emitting element, the present invention relates to a white phosphor capable of emitting white light with a single base material and a white light emitting element using the white phosphor.

  Conventionally, fluorescent lamps and incandescent lamps are used as white light sources. However, these white light sources have problems in terms of power consumption, environmental load due to mercury content, size, operating life, and the like.

  On the other hand, when a light emitting diode (LED) is used as a white light source, it is small and efficient, and a demand as a light emitting element can be expected from the viewpoint of reducing environmental load. Further, since the light emitting diode is a solid element, it has a long operating life, good initial drive characteristics, excellent vibration resistance, and resistance to repeated ON / OFF lighting. For this reason, light emitting diodes have been widely used in various light sources such as various indicators and liquid crystal backlights that consume less power as light emitting elements.

  In recent years, super-bright and high-efficiency red, green, and blue light-emitting diodes have been developed, and large-screen LED displays using these light-emitting diodes as light-emitting elements have been used and can operate with low power. In addition, it has the advantage of being lightweight and having a long life. Under such circumstances, the appearance of a white light emitting device using a light emitting diode as a light emitting element is expected as an alternative to a fluorescent lamp or an incandescent lamp.

  However, when a light emitting diode is used as a light emitting element, in general, the light emitting diode has only a strong monochromatic emission spectrum, and does not have a broad emission spectrum in the visible light range necessary for obtaining white light. There is a problem.

  Therefore, recently, in order to obtain white light, light emitting elements such as light emitting diodes that provide three light components of red, green, and blue are provided close to each other to emit light, and diffused and mixed to produce white light. Has already been used as a large screen LED display.

  However, in this method, the temperature characteristics and temporal changes of the individual diodes are different, so that variations in the color tone, brightness, etc. of each light emission of red, green and blue, or each light emission cannot be uniformly mixed, There are problems such as uneven color, and desired white light cannot be obtained. In addition, since the materials of the respective light emitting diodes are generally different and the driving power is different, it is necessary to apply a predetermined voltage to each of them, which causes a problem that the driving circuit becomes complicated.

  As another method for obtaining white light, light emitted from a light emitting element such as a light emitting diode is absorbed by a phosphor, the absorbed light is converted into light having a different wavelength, and light emission and fluorescence from the light emitting diode are obtained. A method has been proposed in which white light is obtained by diffusive color mixing with light that has been wavelength-converted by a body.

Patent Document 1 (Japanese Patent No. 3503139) uses a nitrogen gallium-based semiconductor containing In as a light-emitting diode (light-emitting element), and uses cerium-activated garnet (Y ₃ Al ₅ O ₁₂ : Ce or the like) as a phosphor. A light emitting device was described.

In this light emitting device, as described above, the light emitting element is an LED chip that is a nitrogen gallium semiconductor containing In and has a light emission peak in a wavelength range of 420 to 490 nm and can emit blue light. As the phosphor, a cerium activated garnet phosphor (Y ₃ Al ₅ O ₁₂ : Ce) is used, and this phosphor absorbs part of the blue emission spectrum and has an emission peak in the vicinity of a wavelength of 510 to 600 nm. . FIG. 7 shows emission spectra of a nitrogen gallium-based semiconductor containing In (blue LED) and a cerium-activated garnet phosphor (Y ₃ Al ₅ O ₁₂ : Ce).

  The white light-emitting device using a combination of this cerium-activated garnet phosphor (YAG: Ce, etc.) and a blue LED consumes less power than fluorescent lamps and does not contain toxic mercury. It is expected as a new white illumination.

  However, this cerium-activated garnet phosphor has a light emission spectrum with a peak in the vicinity of a wavelength of 510 to 600 nm, and therefore has a small red component at a wavelength of 580 to 650 nm and poor color rendering, and an object illuminated by the apparatus is not suitable. It showed a natural hue and had a problem in application to general lighting. The wavelength of the blue component is approximately 400 to 480 nm, and the wavelength of the green component is approximately 480 to 560 nm.

  On the other hand, Patent Document 2 (Japanese Patent Laid-Open No. 2005-201010) describes a light emitting device composed of a blue LED, a green phosphor composition, and a red phosphor composition. In this light emitting device, light emitted from a blue LED (blue light) is received by a green phosphor composition and a red phosphor composition, respectively, and light having a long wavelength (green light and red light) is emitted from each blue LED. White light is obtained by diffusive color mixture of blue light and green light and blue light from the phosphor composition. However, in this light emitting device, since a plurality of phosphors (compositions) are used, it is difficult to adjust the color due to the interaction between the phosphors.

Patent Document 3 (Japanese Patent Laid-Open No. 2001-107044) discloses phosphors having various compositions, but the composition and white phosphor according to the present invention are not specifically specified.

Japanese Patent No. 3503139 Japanese Patent Laid-Open No. 2005-20010 JP 2001-107044 A

  As described above, conventionally, the light emitted from the blue LED is absorbed to show a broad emission spectrum including the green component to the red component, the color adjustment is easy, the color rendering is easy, and natural light (sunlight A phosphor providing white light close to) has not been obtained.

  Accordingly, an object of the present invention is to display a three-wavelength emission spectrum including a blue component to a red component on a single base material for illumination, backlight, special light source, and anti-counterfeit printing, and emit white light. An object of the present invention is to provide a white phosphor that can easily adjust the color, has high color rendering properties, and can obtain white light close to natural light (sunlight).

As a result of intensive studies to solve the above problems, the present inventors have found that the above object can be achieved by a white phosphor having CaZrO ₃ as a crystal base material and Eu ³⁺ and Tb ³⁺ as emission centers. did.

That is, the present invention provides a white phosphor having CaZrO ₃ as a crystal base material and Eu ³⁺ and Tb ³⁺ as emission centers. In the case of obtaining a white phosphor by mixing various conventional phosphors, the present invention emits white light with one kind of phosphor as compared to the case where it is difficult to adjust the color due to the interaction between the phosphors. There is no interaction and there is no burden on manufacturing.

The white phosphor according to the present invention is preferably one represented by the following general formula (1).
Ca _x Zr _y O ₃ : Eu, Tb (1)
(However, 0.8 ≦ x / y ≦ 2.0)

In the white phosphor according to the present invention, the concentrations of Eu ³⁺ and Tb ³⁺ are preferably 0.01 to 10 mol%, more preferably 0.01 to 3 mol%, respectively, with respect to the crystal base material. .

  The white phosphor according to the present invention can contain Pr and Sm as a color adjusting agent in order to improve color rendering.

  The white phosphor according to the present invention may contain one or more elements selected from aluminum group elements such as Al and Ga as a sensitizer for improving excitation efficiency. The content is preferably 5 mol% or less. When the content of these elements exceeds 5 mol%, a large amount of heterogeneous phases are precipitated, and the luminance is remarkably lowered.

  In addition, the white phosphor according to the present invention sensitizes one or more elements selected from rare earth elements such as Sc, Y, La, Gd, and Lu in order to improve the excitation efficiency as described above. It can be contained as an agent. The content is preferably 5 mol% or less. When the content of these elements exceeds 5 mol%, a large amount of heterogeneous phases are precipitated and the luminance is remarkably lowered.

Furthermore, the white phosphor according to the present invention may contain an alkali metal element, a monovalent cation metal such as Ag ⁺ , or a halogen ion such as Cl ⁻ , F ⁻ , or I ⁻ as a charge compensator. The content is preferably the same as the content of the luminescent centers Eu ³⁺ and Tb ³⁺ , that is, 0.01 to 10 mol%, and if it exceeds 10 mol%, the charge compensation effect is lost and the luminance is lowered.

  Further, the present invention provides a mixture containing a calcium compound component, a zirconium compound component, a europium compound component, and a terbium compound component in a quantitative ratio satisfying the formula (1), such as an inert gas such as air, oxygen, Ar, or a hydrogen gas. It is a method for producing a white phosphor, characterized by firing in a reducing gas atmosphere.

  Further, as an additional step, prior to firing, the method for producing a white phosphor according to the above, characterized by calcining in an atmosphere of a reducing gas such as an inert gas such as air, oxygen, or Ar or hydrogen gas It is.

  In the present invention, the firing temperature is 900 to 1300 ° C., the calcination temperature is 800 to 1100 ° C., and the firing or calcination is performed for 1 to 12 hours. It is a manufacturing method of a body.

As is apparent from the fluorescence spectrum, the white phosphor according to the present invention emits light near wavelengths of 420 nm, 540 nm, and 610 nm, and emits light with good color rendering including blue, green, and red components, respectively. . In addition, since CaZrO ₃ is a single crystal base material, there is no interaction and no burden is imposed on the production. It also has excellent reliability and environmental resistance. For this reason, the white phosphor according to the present invention can be applied to general illumination requiring white light close to natural light (sunlight). Further, the white phosphor according to the present invention can be expected as a phosphor for liquid crystal backlights, PDPs, ELs, FEDs, and CRTs in the field of display devices.

Hereinafter, the best mode for carrying out the present invention will be described.
(White phosphor according to the present invention)
The white phosphor according to the present invention is a phosphor having a perovskite structure having CaZrO ₃ as a crystal matrix and Eu ³⁺ and Tb ³⁺ as emission centers.

In the white phosphor according to the present invention, the concentrations of the Eu ³⁺ and Tb ³⁺ that are the emission centers are preferably 0.01 to 10 mol% with respect to the crystal base material, respectively, and 0.01 to 3 mol. % Is more desirable. If the concentration is less than 0.01 mol%, the effect of containing this component is not present, and if it exceeds 10 mol%, a heterogeneous phase is precipitated, and the luminance is significantly reduced.

In the above general formula (1), the content of calcium oxide and / or zirconium oxide represented by Ca _x Zr _y O ₃ which is a crystal base material (0.8 ≦ x / y ≦ 2.0) is expressed as Ca The red component can be increased by increasing the content.

  The white phosphor according to the present invention may contain one or more elements selected from aluminum group elements such as Al and Ga as a sensitizer for improving excitation efficiency. The content is preferably 5 mol% or less. When the content of these elements exceeds 5 mol%, a large amount of heterogeneous phases are precipitated, and the luminance is remarkably lowered.

  In addition, the white phosphor according to the present invention sensitizes one or more elements selected from rare earth elements such as Sc, Y, La, Gd, and Lu in order to improve excitation efficiency as described above. It can be contained as an agent. The content is preferably 5 mol% or less. When the content of these elements exceeds 5 mol%, a large amount of heterogeneous phases are precipitated, and the luminance is remarkably lowered.

Furthermore, the white phosphor according to the present invention may contain an alkali metal element, a monovalent cation metal such as Ag ⁺ , or a halogen ion such as Cl ⁻ , F ⁻ , or I ⁻ as a charge compensator. The content is preferably the same as the content of the luminescent centers Eu ³⁺ and Tb ³⁺ , that is, 0.01 to 10 mol%, and if it exceeds 10 mol%, the charge compensation effect is lost and the luminance is lowered.

  Next, an example of a preferable method for producing the white phosphor according to the present invention will be described.

In the method for producing a white phosphor according to the present invention, the following is preferably used as a raw material.
Ca: CaO, CaCO ₃ etc. Zr: ZrO ₂ , Zr (CO ₃ ) ₂ etc. Eu salt: EuF ₃ , Eu ₂ O ₃ , EuCl ₃ etc. Tb salt: TbF ₃ , Tb ₂ O ₃ , TbCl ₃ etc.

  In the production method according to the present invention, the raw materials are weighed and mixed so as to have a predetermined ratio. For example, the mixing is performed for about 90 minutes with a paint shaker or a ball mill using zirconia balls having a diameter of 3 mm as media.

  Next, the mixed powder and the medium are separated with a sieve of 100 μm or less, and the mixed powder is dried at 80 to 90 ° C. for 5 to 12 hours.

  Next, the mixed powder is calcined in an atmosphere of air, oxygen, Ar, or hydrogen gas at 800 to 1100 ° C. for 1 to 12 hours. When the calcination temperature is less than 800 ° C., when carbonate is used as a raw material, the decomposition of carbon dioxide gas is insufficient, and when a halide is used, a sufficient flux effect cannot be obtained. On the other hand, at a high temperature exceeding 1100 ° C., abnormal grain growth occurs and it becomes difficult to obtain uniform fine particles. Also, if the calcining time is less than 1 hour, it is difficult to obtain reproducibility in the material properties, and if it exceeds 12 hours, there arises a problem of composition variation due to an increase in material scattering.

  After this calcination, the mixture powder is further pulverized and mixed so that the entire mixed powder becomes uniform, and baked again under the same conditions as calcination. That is, baking is performed in an atmosphere of air, oxygen, Ar, or hydrogen gas at 900 to 1300 ° C. for 1 to 12 hours. If the firing time or firing temperature is out of the above range, problems such as a decrease in crystallinity and precipitation of foreign phases occur.

  The white phosphor according to the present invention is a single base material and exhibits an emission spectrum at least in a region of wavelengths of 420 nm ± 70 nm, 540 nm ± 50 nm, and 610 nm ± 20 nm by excitation by any means, from a blue component to a red component. A three-wavelength emission spectrum including Therefore, for example, a white light emitting element can be configured by arranging an ultraviolet light emitter as an excitation light source of a white phosphor in the vicinity of or overlapping with the white phosphor of the present invention. The white phosphor according to the present invention produced in this way can be applied to general illumination, and also in the field of display devices, it can be used for liquid crystal backlights, PDP, EL, FED, CRT, or anti-counterfeit printing. It can also be expected as a body.

  The white phosphor described above can be a white light-emitting element exhibiting high color rendering properties.

  Examples are shown below, but the present invention is not construed as being limited thereto.

Using CaCO ₃ , ZrO _2, EuF ₃ and TbF ₃ as raw materials, the ratio of Ca to Zr (Ca / Zr) is 1.0, the Eu concentration is 0.5 mol% and the Tb concentration is 1 mol with respect to the crystal matrix. %, And this was mixed for 90 minutes with a paint shaker using zirconia balls of 3 mm in diameter as media. Next, the mixed powder and the media were separated with a sieve of 100 μm or less, and dried at 80 ° C. for 6 hours. Next, it was fired in an Ar gas atmosphere at 1300 ° C. for 1 hour to obtain a white phosphor represented by CaZrO ₃ : Eu, Tb (Example 1).

  The fluorescence spectrum of this white phosphor is shown in FIG. As is apparent from FIG. 1, the white phosphor emits light in the vicinity of wavelengths of 420 nm, 540 nm, and 610 nm, and emits light with good color rendering including blue, green, and red components, respectively. Here, it is considered that green and blue light emission is caused by Tb and red light emission is caused by Eu.

(Experiment 1)
Using CaCO ₃ , ZrO ₂ and EuF ₃ as raw materials, the ratio of Ca to Zr (Ca / Zr) is 1.5, and the Eu concentration is 0.5 mol% with respect to the crystal base material. Zirconia balls were used as media and mixed for 90 minutes in a paint shaker. Next, the mixed powder and the media were separated with a sieve of 100 μm or less, and dried at 80 ° C. for 6 hours. Next, it was fired in an Ar gas atmosphere at 1300 ° C. for 1 hour to obtain a phosphor represented by CaZrO ₃ : Eu (Experimental Example 1).

  The fluorescence spectrum of this phosphor is shown in FIG. FIG. 3 shows that the phosphor exhibits weak blue light emission and strong red light emission.

(Experimental example 2)
CaCO ₃ , ZrO ₂ and TbF ₃ are used as raw materials, the ratio of Ca to Zr (Ca / Zr) is 1.0, and the Tb concentration is 1 mol% with respect to the crystal base material. This is zirconia having a diameter of 3 mm. The balls were used as media and mixed for 90 minutes with a paint shaker. Next, the mixed powder and the media were separated with a sieve of 100 μm or less, and dried at 80 ° C. for 6 hours. Next, it was fired in an Ar gas atmosphere at 1300 ° C. for 1 hour to obtain a phosphor represented by CaZrO ₃ : Tb (Experimental Example 2).

  The fluorescence spectrum of this phosphor is shown in FIG. FIG. 4 shows blue light emission and green light emission, but it is understood that red light emission is insufficient.

CaCO ₃ , ZrO ₂ and EuF ₃ are used as raw materials, and the ratio of Ca to Zr (Ca / Zr) is 1.5, and the Eu concentration is 0.5 mol% with respect to the crystal base material. Zirconia balls were used as media and mixed for 90 minutes in a paint shaker. Next, the mixed powder and the media were separated with a sieve of 100 μm or less, and dried at 80 ° C. for 6 hours. Next, it was fired in an oxygen gas atmosphere at 1300 ° C. for 1 hour to obtain a phosphor represented by CaZrO ₃ : Eu (Example 2-1).

CaCO ₃ , ZrO ₂ and TbF ₃ are used as raw materials, the ratio of Ca to Zr (Ca / Zr) is 1.0, and the Tb concentration is 1 mol% with respect to the crystal base material. This is zirconia having a diameter of 3 mm. The balls were used as media and mixed for 90 minutes with a paint shaker. Next, the mixed powder and the media were separated with a sieve of 100 μm or less, and dried at 80 ° C. for 6 hours. Next, it was fired in an Ar gas atmosphere at 1300 ° C. for 1 hour to obtain a phosphor represented by CaZrO ₃ : Tb (Example 2-2).

  The phosphor obtained in Example 2-1 and the phosphor obtained in Example 2-2 were mixed to obtain a white phosphor.

  The fluorescence spectrum of this white phosphor is shown in FIG. As is clear from FIG. 2, this white phosphor has lower emission intensity than that of Example 1, but emits light at wavelengths near 420 nm, 540 nm, and 610 nm, and each of a blue component, a green component, and a red component. Light emission with good color rendering properties including

Comparative Example 1

Gd ₂ O ₂ S and EuF ₃ , TbF ₃ , PrF ₃ are used as raw materials, and the Eu concentration is 0.04 mol%, the Tb concentration is 0.01 mol%, and the Pr concentration is 0.04 mol% with respect to the crystal base material. This was weighed and mixed with a paint shaker for 90 minutes using a zirconia ball having a diameter of 3 mm as a medium. Next, the mixed powder and the media were separated with a sieve of 100 μm or less, and dried at 80 ° C. for 6 hours. Next, it was baked in an Ar gas atmosphere at 1050 ° C. for 12 hours to obtain a phosphor represented by Gd ₂ O ₂ S: Eu, Tb, Pr (Comparative Example 1).

  The fluorescence spectrum of this phosphor is shown in FIG. As is apparent from FIG. 5, this phosphor does not have a sufficient blue component with a wavelength of 380 to 450 nm, and is considered not sufficient as a white phosphor.

Using CaCO ₃ , ZrO ₂ and PrF ₃ as raw materials, the ratio of Ca to Zr (Ca / Zr) is 1.0, and the Pr concentration is 1 mol% with respect to the crystal matrix, and this is zirconia having a diameter of ₃ mm. The balls were used as media and mixed for 90 minutes with a paint shaker. Next, the mixed powder and the media were separated with a sieve of 100 μm or less, and dried at 80 ° C. for 6 hours. Next, 1300 ° C., 1 hour, and fired in an Ar gas atmosphere, CaZrO _3: to obtain a green phosphor represented by Pr (Example 3).

  The fluorescence spectrum of this green phosphor is shown in FIG. The white phosphor according to the present invention can contain Pr as a color adjusting agent that supplements the green component in order to improve color rendering.

CaCO ₃ , ZrO ₂ and SmF ₃ were used as raw materials, and the ratio of Ca to Zr (Ca / Zr) was 1.0, and the Sm concentration was 1 mol% with respect to the crystal base material. Zirconia balls were used as media and mixed for 90 minutes with a paint shaker. Next, the mixed powder and the media were separated with a sieve of 100 μm or less, and dried at 80 ° C. for 6 hours. Next, it was fired in an Ar gas atmosphere at 1300 ° C. for 1 hour to obtain a red phosphor represented by CaZrO ₃ : Sm (Example 4).

  The fluorescence spectrum of this red phosphor is shown in FIG. The white phosphor according to the present invention can contain Sm as a color adjusting agent that supplements the red component in order to improve color rendering.

As is apparent from the fluorescence spectrum, the white phosphor according to the present invention emits light near wavelengths of 420 nm, 540 nm, and 610 nm, and emits light with good color rendering including blue, green, and red components, respectively. . In addition, since CaZrO ₃ is used as a single crystal base material, there is no interaction and no burden is imposed on production. It also has excellent reliability and environmental resistance. For this reason, the white phosphor according to the present invention can be applied to general illumination requiring white light close to natural light (sunlight). In addition, the white phosphor according to the present invention provides a white phosphor that can be expected as a liquid crystal backlight, a phosphor for PDP, EL, FED, and CRT in the field of display devices.

1 is a graph showing the fluorescence spectrum of Example 1. FIG. FIG. 2 is a graph showing the fluorescence spectrum of Example 2. FIG. 3 is a graph showing the fluorescence spectrum of Experimental Example 1. FIG. 4 is a graph showing a fluorescence spectrum of Experimental Example 2. FIG. 5 is a graph showing the fluorescence spectrum of Comparative Example 1. FIG. 6 is a graph showing the fluorescence spectrum of Example 3. FIG. 7 is a graph showing the fluorescence spectrum of Example 4.

Claims (7)

A white phosphor having CaZrO ₃ as a crystal matrix and Eu ³⁺ and Tb ³⁺ as emission centers. A white phosphor represented by the following general formula (1).
Ca _x Zr _y O ₃ : Eu, Tb (1)
(However, 0.8 ≦ x / y ≦ 2.0) 3. The white phosphor according to claim 1, wherein concentrations of Eu ³⁺ and Tb ³⁺ are 0.01 to 10 mol% with respect to the crystal base material. The white light emitting element provided with the structure which uses the white fluorescent substance in any one of Claims 1-3, and an ultraviolet light-emitting body as an excitation light source of this white fluorescent substance.   A mixture containing a calcium compound component, a zirconium compound component, a europium compound component, and a terbium compound component in a quantitative ratio satisfying the formula (1) in an inert gas atmosphere such as air, oxygen, Ar, or a reducing gas atmosphere such as hydrogen gas A method for producing a white phosphor, characterized by firing.   6. The method for producing a white phosphor according to claim 5, wherein, as an additional step, calcining is performed in a reducing gas atmosphere such as an inert gas such as air, oxygen, Ar, or hydrogen gas, before firing. The method for producing a white phosphor according to claim 6, wherein the firing temperature is 900 to 1300 ° C, the calcination temperature is 800 to 1100 ° C, and the firing or calcination is performed for 1 to 12 hours.